The present invention relates in general to a thin film deposition technique employing cathode sputtering, and pertains, more particularly to a co-sputtering cathode system or apparatus for the deposition of doped thin films particularly on large area substrates.
Planar magnetron sputtering has been used as a general purpose technique for the deposition of thin films in both laboratory and production applications. An advantage of planar magnetron sputtering is that it permits relatively high rates of deposition, limits umwanted substrate bombardment and heating, and is particularly adapted for use with large flat substrates without requiring special planetary tooling or excessively large throw distances. Planar magnetron sputtering is characterized by a visible plasma area magnetically confined to a selected region or regions of the cathode which are the only areas with significant emission of sputtered material. The emitting areas or zones assume the form of closed figures in the target plane.
For many applications it is desired to deposit doped films on large area substrates with close control of both uniformity and dopant level. The deposition of doped films has involved the use of a doped target. However, techniques involving doped targets are subject to variations in consistancy of the deposited film particularly over a time span due to concentration or depletion of dopant in the target. Additional disadvantages associated with doped targets are that they may be difficult or impossible to fabricate and that there is a loss in flexibility in changing dopant material or doping level.